Cross-Reference to Related Applications
Reference is made to commonly-assigned U.S. patent application entitled "Dynamic RAM Cell Having Shared Trench Storage Capacitor With Sidewall-Defined Bridge Contacts and Gate Electrodes", Ser. No. 919,940 filed Oct. 17, 1986 by the present inventor and assigned to the assignee of the present invention. This referenced application relates to a trench memory cell in which the polysilicon that fills the trench extends above the surface of the silicon substrate, in order to provide a mandrel upon which both the bridge contacts that couple the polysilicon to an adjacent source diffusion and the gate electrodes of the associated FETS can be defined.
Reference is also made to commonly-assigned U.S. patent application Ser. No. 626,512, entitled "Dynamic RAM Cell with MOS Trench Capacitor in CMOS," filed June 29, 1984 by Lu et al. This application relates to a trench cell in which a polysilicon-filled trench extends through a well region formed on an epitaxial region, into the underlying substrate. The resulting poly-to-substrate storage capacitance is considerably enhanced.
Reference is further made to commonly-assigned U S. patent application Ser. No. 793,401, entitled "High Density Memory," filed Oct. 31, 1985 by the present inventor now U.S. Pat. No. 4,751,558 issued June 14, 1988. This application relates to a DRAM trench cell in which a polycrystalline silicon (polysilicon) capacitor electrode is disposed on the bottom of the trench and the gate electrode of the transfer gate field effect transistor (FET) is disposed on the side wall of the trench so as to define a vertical channel region between the diffused capacitor electrode and the diffused bitline formed on a portion of silicon defined by adjacent trenches.
Finally, reference is made to commonly-assigned U.S. patent application Ser. No. 885,618, entitled "Two Square Memory Cells," filed July 15, 1986 by Garnache et al now U.S. Pat. No. 4,769,786 issued Sept. 6, 1988. This application relates to a DRAM trench cell in which the bottom portion of the trench is filled with polysilicon to define separate storage capacitors on each side of the trench, and the upper portion of the trench has gate electrodes so that a conductive channel is formed along the side walls of the trench.